It would vary with the terrain, of course; one of my family’s amusements with maps consists of verifying the “40 km hypothesis”, that on the easy to travel parts of Spain if you have a biggish town in a certain spot there will be other biggish towns at about 40km on each major road. Smaller towns at the 20km markers. My ancestral home village is 10km from the capital and it used to be considered “close enough to go, run one errand and come back in the day, under good conditions”; distant enough that the family usually kept a house in the capital (you know, in case they needed to run two errands).
When traveling over the mountains, “get over the pass and to the next village” was and still is considered good enough: the distance from St Jean Pied de Port to Roncesvalles Abbey is 30km and many people think they’ll be able to do that comfortably (many think they can go all the way to Pamplona, 40km further), yet very often they end up getting from the top of the pass to the abbey in the abbot’s van, too tired to even wonder out loud when did their legs atomize.
At the time of the Dutch wars of independence, the Spanish Crown was unable to send gold by either land or sea. This led to a collapse of credit for the Spanish Crown, and an inability to pay for civilian government or military effort.
Samuel Pepys records doing the 55 miles from London to his relatives at Brampton. He could do it in a day if necessary, (such as when he heard his wealthy uncle, from whom he had ‘expectations’, had died) by riding post, hiring fresh mounts from the posthouses on the road. He would ride to the next post town (10-15 miles), with a postboy to guide him and to take the horses back again, and there obtain a fresh horse. This method was expensive and normally the cost would not be justified. More commonly he spent the night at an inn and completed the journey the following day. His speed was about 4 miles an hour in summer and less in winter.
The condition of even major roads was a continual source of complaint for travellers. The inhabitants of each parish were supposed to perform six days labour on the roads every year. Not surprisingly, the work was badly done, if it was done at all, and mostly consisted in filling in holes. Often a traveller would be presented with a variety of possible tracks from previous travellers’ efforts to detour around the worst bits and Pepys himself got lost on a road he had travelled many times.
A healthy, physically fit man can walk 20-25 miles a day. (I’ve done it and it was NOT fun.) That means walking all day, while still taking the time to rest, eat, make camp, etc. Going beyond this invites exhaustion and injury. Of course, this also depends on the roads and the weather and things like that.
Weirdly, traveling by horse doesn’t really improve things. A horse can average about 20 miles a day. Soldiers in the 19th century observed that infantry could actually outpace cavalry over time. This likewise assumes you are making time for rest, feeding, and maintenance of the animal. As Mk VII points out, riding Pony Express style by acquiring remounts can speed things up.